You need a web gateway that is able to integrate with your user database. So you can block certain users from certain websites and downloads, monitor who went on which website, etc. Or you can invest in a gateway firewall that does similar filtering and can also block certain apps from getting out to the internet as well. This is because they have a list of application signatures. Here is a list of web gateways if anyone looking into one. http://jafsec.com/Web-Security/Secure-Web-Gateway-A-B.html